The known antibiotic nogalamycin, and a process for its preparation, are described in U.S. Pat. No. 3,183,157. The structure of nogalamycin can be shown as follows: ##STR1##
Antibiotics nogalarol and nogalarene, produced by acid hydrolysis of nogalamycin, and o-methylnogalarol, produced by acidic methanolysis of nogalamycin or nogalarol, are disclosed in U.S. Pat. No. 3,501,569.